The present invention relates to heat sinking techniques and assemblies for use in connection with circuit boards and more particularly to a technique and structure for significantly increasing the heat dissipating capabilities of a printed circuit assembly.
One of the major problems encountered in the prior art construction and use of printed circuits is the inability to effectively dissipate heat generated by the components in a particular electronic apparatus. As the technology advances and greater numbers of components are used in connection with individual printed circuit boards, more heat will be generated than is capable of being dissipated by conventional heat sinking techniques. The heat sinking capability is further decreased by the assembly configurations of such structures which often require a plurality of closely stacked printed circuit boards that allow little room for convection cooling or conventional heat dissipating fins or large heat dissipating attachments. Naturally, any addition of heat dissipating structures of large size would defeat attempts to provide more components in smaller areas for reducing the size of the electronic devices in which the boards are employed.
Various attempts have been made to overcome the problems created by the heat generated in printed circuits by the associated electronic components. In one such technique, the electrically conductive areas on the printed circuit boards were increased in size to provide a greater area for radiating heat. Rather than using small conductive areas to interconnect the terminals to which the electronic components are attached, the conductive areas are made larger and only thin insulating strips are formed between those conductive areas. Any heat generated by the electronic components and transferred to the conductive areas is then radiated from a larger area and capable of more efficiently dissipating the heat. Alternatively, a conductive backing plate can be applied to an opposite side of the circuit board. The backing plate is configured to have insulating areas in the region of the respective terminals, which allows the conductive plate to be attached to the opposite side of the printed circuit board to enhance heat dissipation. In both cases, the heat dissipation is allegedly improved by the increase in radiating surface area produced by the increased size in the conductive surface areas. While the above technique may be effective in reducing heat build-up and improving heat dissipation, the same relies primarily upon air convection to dissipate heat and requires special techniques to form the conductive areas and backing plate.
In another prior art technique, a thermally conducting cushion-like elastomeric pad is molded with recesses on one surface to fit over the electronic components on a printed circuit board. The opposite surface of the cushion is maintained in contact with a heatsink and the heat generated in the electronic components is then transferred through the pad and removed by the heatsink. While this technique may also improve the heat dissipating capabilities of the printed circuit assembly, the process of forming the recesses is complicated and the size of the thermal pad and required heatsink prevents close spacing of the printed circuit boards or a reduction in their size for more compact construction.
In still other prior art techniques, thermally conductive pads are physically attached to selected areas on the side of circuit boards opposite to that containing the circuit components. In this example, the opposite surface of the circuit module is fabricated to include various geometric pads which correspond to the shapes of the electronic components on the circuit surface. The module is then dip-soldered to produce a projection whose shape is similar to that of the pad geometry. The projections formed on the surface of the module then provide a plurality of heatsinks having various shapes and sizes for dissipating heat produced by the electronic components. While improvements in heat dissipation may be achieved using this technique, the forming process is complex and the structure primarily relies on surface convection for cooling.
Although each of the above techniques attempt to provide improved heat dissipating capabilities, the same require numerous fabrication steps and each is restricted to particular board geometries and types. There is therefore a continuing need for techniques and assemblies which can be easily performed and constructed, yet provide more effective heat dissipation in environments requiring more closely spaced boards and a greater number of components. Accordingly, the invention has been developed to overcome the shortcomings of the above known and similar techniques and to provide a heat dissipating tehcnique and printed circuit heatsink assembly which is easily fabricated using simplified procedures.